| Sodium nitroprusside | |
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Sodium pentacyanonitrosylferrate(II) |
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Other names
Sodium nitroprusside |
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| Identifiers | |
| CAS number | 14402-89-2 , (anhydrous) 13755-38-9 (dihydrate) |
| PubChem | 26256 |
| EC number | 238-373-9 |
| DrugBank | APRD01143 |
| ChEMBL | CHEMBL136478 , CHEMBL74115 |
| RTECS number | LJ8750000 |
| ATC code | C02 |
| Properties | |
| Molecular formula | Na2[Fe(CN)5NO] |
| Molar mass | 261.92 g/mol (anhydrous) 297.95 g/mol (dihydrate) |
| Appearance | red powder |
| Solubility in water | good |
| Solubility in ethanol | soluble |
| Structure | |
| Coordination geometry |
octahedral at Fe |
| Pharmacology | |
| Routes of administration |
Intravenous |
| Metabolism | Circulatory |
| Elimination half-life |
2 minutes (metabolites: several days) |
| Excretion | Renal |
| Legal status |
℞ Prescription only |
| Pregnancy category |
C |
| Hazards | |
| EU Index | Not listed |
| Flash point | Non-flammable |
| (verify) (what is: /?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| Infobox references | |
Sodium nitroprusside is the inorganic compound with the formula Na2[Fe(CN)5NO]·2H2O.[1] This red-coloured salt, which is often abbreviated SNP, is a potent vasodilator. The sodium salt dissolves in water and to a lesser extent in ethanol to give solutions containing the dianion [Fe(CN)5NO]2−.
Contents |
Nitroprusside is a complex anion that features an octahedral ferrous centre surrounded by five tightly bound cyanide ligands and one linear nitric oxide ligand. The molecular symmetry is C4v. Linear nitrosyl ligands are assigned a single positive charge, thus the iron is assigned an oxidation state of 2+. As such it has a low-spin d6 electron configuration and is diamagnetic. Its chemical reactions are mainly associated with the NO ligand.[2]
Sodium nitroprusside (Abbreviated SNP, brand name: Nitropress) has potent vasodilating effects in arterioles and venules (arterioles more than venules). It is administered intravenously in cases of acute hypertensive emergency. SNP breaks down in circulation to release nitric oxide (NO). NO activates guanylate cyclase in vascular smooth muscle and increases intracellular production of cGMP. cGMP stimulates calcium movement from the cytoplasm to the endoplasmic reticulum and reduces calcium available to bind with calmodulin. Vascular smooth muscle relaxes, which allow vessels to dilate.
In the human heart, nitric oxide reduces both total peripheral resistance as well as venous return, thus decreasing both preload and afterload. For this reason, it can be used in severe cardiogenic heart failure where this combination of effects can act to increase cardiac output. In situations where cardiac output is normal, the effect is to reduce blood pressure.
Sodium nitroprusside slowly breaks down to release 5 cyanide ions, especially upon exposure to UV light. Despite the toxic potential of cyanide, nitroprusside remains an effective drug in certain clinical circumstances such as malignant hypertension or for rapid control of blood pressure during vascular surgery and neurosurgery. The cyanide can be detoxified by reaction with a sulfur-donor such as thiosulfate, catalysed by the enzyme rhodanese. In the absence of sufficient thiosulfate, cyanide ions can quickly reach toxic levels.[4] The half-life of nitroprusside is 1–2 minutes, but the metabolite thiocyanate has an excretion half-life of several days.
In physiology research, sodium nitroprusside is frequently used to test endothelium-independent vasodilation. Iontophoresis, for example, allows local administration of the drug, preventing the systemic effects listed above but still inducing local microvascular vasodilation.
Sodium nitroprusside is also used in the presence of buffers as a reagent for ketone strips, which test the ketone levels in the urine of a diabetic. Colour change on the strip indicates the relative concentration of ketones.
Sodium nitroprusside is often used as a reference compound for the calibration of Mössbauer spectrometer. It is also used as an analytical reagent in qualitative organic analysis.
In combination with acetaldehyde it is also used as a colour reagent in the development of thin layer chromtography plates, particularly for N-heterocyclic compounds.
Sodium nitroprusside is also used in a urinalysis test, called the cyanide nitroprusside test, also known as Brand's test. In this test sodium cyanide is added first to urine and let stand for approximately 10 minutes. In this time disulfide bonds will be broken by the released cyanide. The destruction of disulfide bonds liberates cysteine from cystine and homocysteine from homocystine. Next sodium nitroprusside is added to the solution and it reacts with the newly freed sulfhydryl groups. The test will turn a red/purple colour if the test is positive indicating that there was significant amounts of amino acid in the urine (aminoaciduria). Cysteine, cystine, homocysteine and homocystine all react when present in the urine when this test is performed. This test can indicate inborn errors of amino acid transporters such as cystinuria, which results from pathology in the transport of dibasic amino acids.
SNP is also used in microbiology, where it has been linked with the dispersal of Pseudomonas aeruginosa biofilms by acting as a nitric oxide donor.[5]
Sodium nitroprusside is used by forensic chemists in a preliminary test in the identification of illicit substances.[6] The test, called Simon's test, is performed by adding 1 volume of a solution of SNP and acetaldehyde in deionized water to a suspected drug, followed by the addition of 2 volumes of an aqueous sodium carbonate solution. The test turns blue for some secondary amines. The most common secondary amines encountered in forensic chemistry include 3,4-methylenedixoymethamphetamine (MDMA, the main component in Ecstasy), and phenethylamines such as methamphetamine and amphetamine.
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